llvm optimizes with library functions

Question

Starting with code like this

void lib_memset( unsigned char *dest, unsigned char c, unsigned int n)
{
    while(n--)
    {
        *dest=c;
        dest++;
          


        

Answer 1

I encounter the same problem and if it still can help anyone this is what I did to solve it - I modify the LoopIdiomRecognize.cpp file in the llvm source code: there is a code that checks if the name of the function is memset or memcpy it cancel the optimization, so I changed it from:

StringRef Name = L->getHeader()->getParent()->getName();
  if (Name == "memset" || Name == "memcpy")

to

StringRef Name = L->getHeader()->getParent()->getName();
  if (Name.endswith("memset") || Name == "memcpy")